Mike Williams tore a muscle in his right foot in the Washington Redskins’ loss to the Dallas Cowboys on Sunday and won’t play in the season finale Sunday at the San Diego Chargers.

So the 4-11 Redskins will close out a horrid season by making yet another change on the offensive line - the seventh move in 14 games at the right guard spot.

Coach Jim Zorn has yet to decide whether Will Montgomery will start against the Chargers. Montgomery started at right guard in Weeks 6 and 7 and replaced Williams in the second quarter against Dallas.

Rookie free agent Edwin Williams, who started Week 12, and Paul Fanaika, signed off the Philadelphia Eagles’ practice squad last month, are the other guards on the roster aside from starting left guard Derrick Dockery.

“I think I was playing with it for a while,” Mike Williams said of the injury. “We’ve been dealing with a lot of stuff. If it’s not this foot, it’s the other one.”

Williams, who isn’t expected to need surgery, missed Weeks 10 and 11 with a sprained left ankle.

One lineman already on injured reserve, six-time Pro Bowl tackle Chris Samuels, expects to learn soon whether his career will be over after 10 seasons.

“I’m feeling great,” said the 32-year-old Samuels, whose season ended with a neck injury in Week 5. “Pretty shortly after the season’s over, I’ll get another MRI, see the doctor and make a decision about what I gotta do.”

Right tackle Stephon Heyer, who went out briefly in the third quarter with an injured right patellar tendon, is expected to remain in the lineup.

On the defensive side of the ball, safety Reed Doughty almost certainly won’t play after suffering a high right ankle sprain Sunday. Kareem Moore is likely to make his second career start at safety in Doughty’s place.

Weakside linebacker Rocky McIntosh, who exited in the third quarter with back spasms, is also expected to play.

“I’ll be all right,” McIntosh said after the game. “It just went out on me when I was covering a pass.”

Zorn said receiver Devin Thomas, who didn’t play against the Cowboys because of a sprained right ankle suffered against the New York Giants last week, could return against the Chargers.

Effort in question

Co-captain Cornelius Griffin wasn’t pleased with the effort of some of his teammates in losses to the Cowboys and Giants by a combined score of 62-12.

Zorn said he liked the team’s effort against Dallas and expects the same this week.

“Our players played hard,” Zorn said. “I didn’t have any depression or holding my breath about the kind of effort that we gave. … They’re professional. They’re playing for the offseason right now.”

A rare bright spot

The Redskins, a top-10 defense during four of the previous five seasons, rank 11th this season. Washington is tied for 16th in scoring defense and 20th against the run.

But as they showed again against the Cowboys, no team is better on fourth down than the Redskins. Washington stopped running back Marion Barber cold twice on fourth down, raising its success rate to 11 of 14, a league-best 81.2 percent.

“Our defense really came out and played with passion,” Zorn said. “They had a couple really good fourth-down holds and gave us some field position.”